Simula introduced the concept of the class in its 1967 version, Simula 67.
Norwegian computer scientists Ole-Johan Dahl and Kristen Nygaard created Simula at the Norwegian Computing Center. They initially designed Simula to model complex systems, such as industrial processes, using entities that could retain state and behavior. The language evolved from Simula I into Simula 67.
Simula 67 introduced classes, objects, inheritance, and virtual methods in a form that strongly influenced object-oriented programming. A class could describe the structure and behavior of objects, while individual objects represented particular instances of that description.
Later languages borrowed or developed these ideas in different ways. Smalltalk made object-oriented programming central to its environment, while C++ added object-oriented features to C. Simula is therefore historically important even though it is not as widely used today as mainstream languages descended from or influenced by its design.